1. Field of the Invention
The invention discloses a method and apparatus for controlling the transformation of Shape Memory Alloy, particularly a precision control method and apparatus applied to the transformation of Shape Memory Alloy.
2. Description of the Prior Art
In the medical field, there many substitutes for human function, or the auxiliary electromechanical equipments, such as the artificial limb, pacemaker, artificial electronic ear and artificial knee etc. are the focal research point in many research fields. However, most auxiliary electromechanical equipments are controlled by the motor at present, there are some shortcomings such as large occupation volume, unable to be used for a long time, generation of noise, and apt to break down etc. Thus it is the future trend to select the Shape Memory Alloy (SMA) to substitute the motor, so that the auxiliary or integrated artificial organs will be more suitable to be used for the patients, or carry out the relevant medical therapy.
The SMA is a kind of an alloy having the shape memory effect; it is the functional material which can remember the original shape of design. The ordinary material will be deformed by the external force under the specific temperature, and then it will turn into the deformed shape after the external force is removed. Even the SMA will also be deformed by the external force under the specific temperature, thought it can recover to its original shape automatically under the higher temperature. Comparing to the use of the motor, the SMA will not generate the permanent magnetism and sparking, and will have the advantages such as low temperature, quiet, uneasy to get metal fatigue etc. Thus the SMA is often applied to a narrower space at present, or to the machines and equipments with higher requirement. However, due to the flexible amount of SMA is unable to be controlled effectively; it is still unable to be applied to various equipments required precision control at present.
The SMA can be changed via temperature or current. It can be applied to the transmission control due to its shape transformation. At present, the control method of SMA is the only linear two-stage way. Only stretching and contracting states are unable to satisfy various demands. The SMA only has binary-valve value transformation characteristics; it is unable to carry on precision control of flex amount, thus it is relatively shortage of flexible control for the application.
Therefore, under the control technology of the existing SMA is unable to reach effective application, the advanced research and development of SMA control technology will be more important for the future.